(WCMH) – FEMA has an unusual way to unofficially predict how bad a natural disaster could be.

It’s called the ‘Waffle House Index.’

It works like this. Waffle House is known for being open 24-hours a day, no matter what. Anytime a Waffle House shuts down, it suggests a really bad natural disaster with devastating effects on the economy.

“So if a Waffle House is open we knew it wasn’t too bad to keep going, if it was open with a limited menu we probably had a lot of power outages and needed to be prepared to support mass care,” said FEMA administrator Craig Fugate. “So if a Waffle House is closed that’s a pretty bad indicator and I believe Waffle Houses are closing in advance of the storm so in Florida I think that helped a lot of people understand that nobody was kidding around that this storm was bad.

According to a tweet this morning from Waffle House, 25 of its restaurant locations in Florida, Georgia and South Carolina have closed their doors due to the storm.

For reference, five years ago, 22 Waffle Houses closed due to Hurricane Irene.

Irene turned out to be one of the top 10 costliest hurricanes in U.S. history.